Electrochemical energy storage devices

ABSTRACT

Pressure relief mechanisms can provide an outlet for cathode pressure buildup during battery operation. Mechanical cathode modifications can control cathode interfaces during battery operation. Pressure relief mechanisms and mechanical modifications can be utilized to improve performance, longevity and/or to prevent failure of batteries, such as during cycling of liquid metal batteries.

CROSS-REFERENCE

This application is a continuation application of U.S. patentapplication Ser. No. 14/178,806, filed Feb. 12, 2014, which claims thebenefit of U.S. Provisional Application No. 61/763,925, filed Feb. 12,2013, each of which is entirely incorporated herein by reference.

BACKGROUND

A battery is a device capable of converting chemical energy intoelectrical energy. Batteries are used in many household and industrialapplications. In some instances, batteries are rechargeable such thatelectrical energy (e.g., converted from non-electrical types of energysuch as mechanical energy) is capable of being stored in the battery aschemical energy, i.e., by charging the battery.

SUMMARY

This disclosure provides energy storage devices and systems. An energystorage device can include a negative electrode, a liquid electrolyteand a positive electrode. In some situations, during discharge of theenergy storage device, an intermetallic layer forms between the positiveelectrode and the electrolyte. The intermetallic layer can be solid orsemi-solid. During discharge of the energy storage device, theintermetallic layer can bulge towards the negative electrode. In somesituations, contact between the intermetallic layer and the negativeelectrode can cause a short in the energy storage device, which may notbe preferable. Recognized herein is the need to prevent such a short.

Energy storage devices of the disclosure can include features that areconfigured to prevent a shorting between the intermetallic layer and thenegative electrode, which may occur upon discharging an energy storagedevice. For instance, one or more posts can be provided between positiveelectrodes to minimize, or prevent, the intermetallic layer from bulgingtowards the negative electrode and shorting with the negative electrode.As another example, one or more pipes (e.g., riser pipes) can beprovided to provide a pressure relieve mechanism for the positiveelectrode. The one or more riser pipes can aid in relieving pressure inthe positive electrode, thereby minimizing, if not preventing, theintermetallic layer from bulging towards the negative electrode andshorting with the negative electrode.

An aspect of the present disclosure provides an energy storage devicecomprising a first electrode comprising a first material, a secondelectrode comprising a second material, and a liquid electrolyte betweenthe first and second electrodes. The liquid electrolyte is capable ofconducting ions from the first material. Upon discharge of the energystorage device, the first and second materials react to form anintermetallic layer at an interface between the second electrode and theelectrolyte. The energy storage device can further comprises one or moreattachment points adjacent to the second electrode. The one or moreattachment points anchor the intermetallic layer.

Another aspect of the present disclosure provides an energy storagedevice comprising a liquid metal electrode adjacent to an electrolyte,and an attachment point that interacts with an intermetallic layerformed at an interface of the electrolyte and the liquid metal electrodeduring discharge of the energy storage device. A structural feature ofthe intermetallic layer can change upon interaction with the attachmentpoint.

Another aspect of the present disclosure provides an energy storagedevice comprising a first chamber comprising a liquid metal electrode,and a second chamber in fluid communication with the first chamber. Thesecond chamber is adapted to allow the liquid metal electrode to expandinto the second chamber during charge/discharge of the energy storagedevice.

Additional aspects and advantages of the present disclosure will becomereadily apparent to those skilled in this art from the followingdetailed description, wherein only illustrative embodiments of thepresent disclosure are shown and described. As will be realized, thepresent disclosure is capable of other and different embodiments, andits several details are capable of modifications in various obviousrespects, all without departing from the disclosure. Accordingly, thedrawings and description are to be regarded as illustrative in nature,and not as restrictive.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings or figures (also “FIG.” and “FIGS.” herein), ofwhich:

FIG. 1 is an illustration of an electrochemical cell and a compilation(i.e., battery) of electrochemical cells;

FIG. 2 is a schematic cross-sectional illustration of a housing having aconductor in electrical communication with a current collector passingthrough an aperture in the housing;

FIG. 3 is a cross-sectional side view of an electrochemical cell orbattery;

FIG. 4 is a cross-sectional side view of an electrochemical cell orbattery with an intermetallic layer;

FIG. 5 is a cross-sectional side view of an electrochemical cell orbattery with a pressure relief structure;

FIGS. 6A and 6B are cross-sectional side and bottom views ofelectrochemical cells or batteries with alternative pressure reliefstructures;

FIG. 7A a cross-sectional side view of an electrochemical cell orbattery with a bowing or bulging solid intermetallic layer;

FIG. 7B is a cross-sectional side view of the electrochemical cell orbattery with a post; and

FIG. 7C is a cross-sectional side view of the electrochemical cell orbattery with ridges.

DETAILED DESCRIPTION

While various embodiments of the invention have been shown and describedherein, it will be obvious to those skilled in the art that suchembodiments are provided by way of example only. Numerous variations,changes, and substitutions may occur to those skilled in the art withoutdeparting from the invention. It should be understood that variousalternatives to the embodiments of the invention described herein may beemployed. It shall be understood that different aspects of the inventioncan be appreciated individually, collectively, or in combination witheach other.

This disclosure provides electrochemical energy storage devices (orbatteries) and electrochemical battery housings. An electrochemicalbattery generally includes an electrochemical battery cell sealed (e.g.,hermetically sealed) within an electrochemical battery housing.

The term “cell,” as used herein, generally refers to an electrochemicalcell. A cell can include a negative electrode of material ‘A’ and apositive electrode of material ‘B’, denoted as A∥B. The positive andnegative electrodes can be separated by an electrolyte. A cell can alsoinclude a housing, one or more current collectors, and a hightemperature electrically isolating seal.

The term “module,” as used herein, generally refers to cells that areattached together in parallel by, for example, mechanically connectingthe cell housing of one cell with the cell housing of an adjacent cell(e.g., cells that are connected together in an approximately horizontalpacking plane). A module can include a plurality of cells in parallel. Amodule can comprise any number of cells (e.g., 2, 3, 4, 5, 6, 7, 8, 9,10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or more). In some cases, amodule comprises 4, 9, 12, or 16 cells. In some cases, a module iscapable of storing about 700 Watt-hours of energy and/or deliveringabout 175 Watts of power.

The term “pack,” as used herein, generally refers to modules that areattached through different electrical connections (e.g., vertically andin series or parallel). A pack can comprise any number of modules (e.g.,1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20,or more). In some cases, a pack comprises 3 modules. In some cases, apack is capable of storing about 2 kilowatt-hours of energy and/ordelivering about 0.5 kilowatts of power.

The term “core,” as used herein generally refers to a plurality ofmodules or packs that are attached through different electricalconnections (e.g., in series and/or parallel). A core can comprise anynumber of modules or packs (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,13, 14, 15, 16, 17, 18, 19, 20, or more). In some cases, the core alsocomprises mechanical, electrical, and thermal systems that allow thecore to efficiently store and return electrical energy in a controlledmanner. In some cases, a core comprises 12 packs. In some cases, a coreis capable of storing about 35 kilowatt-hours of energy and/ordelivering about 7 kilowatts of power.

The term “pod,” as used herein, generally refers to a plurality of coresthat are attached through different electrical connections (e.g., inseries and/or parallel). A pod can comprise any number of cores (e.g.,1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20,or more). In some cases, the pod contains cores that are connected inparallel with appropriate by-pass electronic circuitry, thus enabling acore to be disconnected while continuing to allow the other cores tostore and return energy. In some cases, a pod comprises 4 cores. In somecases, a pod is capable of storing about 100 kilowatt-hours of energyand/or delivering about 25 kilowatts of power.

The term “system,” as used herein, generally refers to a plurality ofcores or pods that are attached through different electrical connections(e.g., in series and/or parallel). A system can comprise any number ofcores or pods (e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,17, 18, 19, 20, or more). In some cases, a system comprises 20 pods. Insome cases, a system is capable of storing about 2 megawatt-hours ofenergy and/or delivering about 500 kilowatts of power.

The term “battery,” as used herein, generally refers to one or moreelectrochemical cells connected in series and/or parallel. A battery cancomprise any number of electrochemical cells, modules, packs, cores,pods or systems.

The term “vertical,” as used herein, generally refers to a directionthat is parallel to the gravitational acceleration vector (g).

The term “cycle,” as used herein, generally refers to a charge/dischargeor discharge/charge cycle.

Electrochemical Energy Storage

The present disclosure provides electrochemical energy storage devices(e.g., batteries) and systems. An electrochemical energy storage devicegenerally includes at least one electrochemical cell, also “cell” and“battery cell” herein, sealed (e.g., hermetically sealed) within ahousing. A cell can be configured to deliver electrical energy (e.g.,electrons under potential) to a load, such as, for example, anelectronic device, another energy storage device or a power grid.

An electrochemical cell of the disclosure can include a negativeelectrode, an electrolyte adjacent to the negative electrode, and apositive electrode adjacent to the electrolyte. The negative electrodecan be separated from the positive electrode by the electrolyte. Thenegative electrode can be an anode during discharge. The positiveelectrode can be a cathode during discharge. In some examples, anelectrochemical cell is a liquid metal battery cell. In some examples, aliquid metal battery cell can include a liquid electrolyte arrangedbetween a negative liquid (e.g., molten) metal electrode and a positiveliquid (e.g., molten) metal, metalloid and/or non-metal electrode. Insome cases, a liquid metal battery cell has a molten alkali metal (e.g.,lithium, magnesium, sodium) negative electrode, an electrolyte, and amolten metal positive electrode. The molten metal positive electrode caninclude one or more of tin, lead, bismuth, antimony, tellurium andselenium. Any description of a metal or molten metal positive electrode,or a positive electrode, herein may refer to an electrode including oneor more of a metal, a metalloid and a non-metal. The positive electrodemay contain one or more of the listed examples of materials. In anexample, the molten metal positive electrode can include lead andantimony. In some examples, the molten metal positive electrode mayinclude an alkali metal alloyed in the positive electrode.

In some examples, an electrochemical energy storage device includes aliquid metal negative electrode, a liquid metal positive electrode, anda liquid metal electrolyte separating the liquid metal negativeelectrode and the liquid metal positive electrode. The negativeelectrode can include an alkali or alkaline earth metal, such aslithium, sodium, potassium, rubidium, cesium, magnesium, barium,calcium, sodium, or combinations thereof. The positive electrode caninclude elements selected from transition metals or d-block elements(e.g., Group 12), Group IIIA, IVA, VA and VIA of the periodic table ofthe elements, such as zinc, cadmium, mercury, aluminum, gallium, indium,silicon, germanium, tin, lead, pnicogens (e.g., arsenic, bismuth andantimony), chalcogens (e.g., tellurium and selenium), or combinationsthereof. In some examples, the positive electrode comprises a Group 12element of the periodic table of the elements, such as one or more ofzinc (Zn), cadmium (Cd) and mercury (Hg). The electrolyte can include asalt (e.g., molten salt), such as an alkali metal salt. The alkali oralkaline earth metal salt can be a halide, such as a fluoride, chloride,bromide, or iodide of the active alkali metal, or combinations thereof.In an example, the electrolyte includes lithium chloride. As analternative, the salt of the active alkali metal can be, for example, anon-chloride halide, bistriflimide, fluorosulfano-amine, perchlorate,hexaflourophosphate, tetrafluoroborate, carbonate, hydroxide, nitrates,nitrites, sulfates, sulfites, or combinations thereof.

In some cases, the negative electrode and the positive electrode of anelectrochemical energy storage device are in the liquid state at anoperating temperature of the energy storage device. To maintain theelectrodes in the liquid states, the battery cell may be heated to anysuitable temperature. In some examples, the battery cell is heated toand/or maintained at a temperature of about 100° C., about 150° C.,about 200° C., about 250° C., about 300° C., about 350° C., about 400°C., about 450° C., about 500° C., about 550° C., about 600° C., about650° C., or about 700° C. The battery cell may be heated to and/ormaintained at a temperature of at least about 100° C., at least about150° C., at least about 200° C., at least about 250° C., at least about300° C., at least about 350° C., at least about 400° C., at least about450° C., at least about 500° C., at least about 550° C., at least about600° C., at least about 650° C., or at least about 700° C. In somesituations, the battery cell is heated to between 200° C. and about 600°C., or between about 450° C. and 575° C.

Electrochemical cells of the disclosure may be adapted to cycle betweencharged (or energy storage) modes and discharged (or energy release)modes. In some examples, an electrochemical cell can be fully charged,partially charged or partially discharged, or fully discharged.

In some implementations, during a charging mode of an electrochemicalenergy storage device, electrical current received from an externalpower source (e.g., a generator or an electrical grid) may cause metalatoms in the metal positive electrode to release one or more electrons,dissolving into the electrolyte as a positively charged ion (i.e.,cation). Simultaneously, cations of the same species or cations of adifferent species can migrate through the electrolyte and may acceptelectrons at the negative electrode, causing the cations to transitionto a neutral metal species, thereby adding to the mass of the negativeelectrode. The removal of the active metal species from the positiveelectrode and the addition of the active metal to the negative electrodestores electrochemical energy. During an energy discharge mode, anelectrical load is coupled to the electrodes and the previously addedmetal species in the negative electrode can be released from the metalnegative electrode, pass through the electrolyte as ions, and deposit asa neutral species with the positive electrode (and in some cases alloywith the positive electrode material), with the flow of ions accompaniedby the external and matching flow of electrons through the externalcircuit/load. This electrochemically facilitated metal alloying reactiondischarges the previously stored electrochemical energy to theelectrical load.

In a charged state, the negative electrode can include negativeelectrode material and the positive electrode can include positiveelectrode material. During discharging (e.g., when the battery iscoupled to a load), the negative electrode material yields one or moreelectrons, and cations of the negative electrode material.Simultaneously, ions of the positive metal species accept electrons atthe positive electrode and deposit as a metal on the positive electrode.The cations migrate through the electrolyte to the positive electrodematerial and react with the positive electrode material to form analloy. During charging, the alloy at the positive electrodedisassociates to yield cations of the negative electrode material, whichmigrates through the electrolyte to the negative electrode.

In some examples, ions can migrate through an electrolyte from an anodeto a cathode, or vice versa. In some cases, ions can migrate through anelectrolyte in a push-pop fashion in which an entering ion of one typeejects an ion of the same type from the electrolyte. For example, duringdischarge, a lithium anode and a lithium chloride electrolyte cancontribute a lithium cation to a cathode by a process in which a lithiumcation formed at the anode interacts with the electrolyte to eject alithium cation from the electrolyte into the cathode. The lithium cationformed at the anode in such a case may not necessarily migrate throughthe electrolyte to the cathode. The cation can be formed at an interfacebetween the anode and the electrolyte, and accepted at an interface ofthe cathode and the electrolyte.

The present disclosure provides Type 1 and Type 2 cells, which can varybased on, and be defined by, the composition of the active components(e.g., negative electrode, electrolyte and positive electrode), andbased on the mode of operation of the cells (e.g., low voltage modeversus high voltage mode).

In an example Type 1 cell, upon discharging, cations formed at thenegative electrode can migrate into the electrolyte. Concurrently, theelectrolyte can provide a cation of the same species (e.g., the cationof the negative electrode material) to the positive electrode, which canreduce from a cation to a neutrally charged metallic species, and alloywith the positive electrode. In a discharged state, the negativeelectrode can be depleted of the negative electrode material (e.g., Na,Li, Ca, Mg). During charging, the alloy at the positive electrodedisassociates to yield cations of the negative electrode material (e.g.Na⁺, Li⁺, Ca²⁺, Mg²⁺), which migrate into the electrolyte. Theelectrolyte can then provide cations (e.g., the cation of the negativeelectrode material) to the negative electrode, which replenishes thenegative electrode to provide a cell in a charged state. A Type 1 cellcan operate in a push-pop fashion, in which the entry of a cation intothe electrolyte results in the discharge of the same cation from theelectrolyte.

In an example Type 2 cell, in a discharged state the electrolytecomprises cations of the negative electrode material (e.g., Na⁺, Li⁺,Ca²⁺, Mg²⁺), and the positive electrode comprises positive electrodematerial (e.g., Pb, Sn, Zn, Hg). During charging, a cation of thenegative electrode material from the electrolyte accepts one or moreelectrons (e.g., from a negative current collector) to form the negativeelectrode comprising the negative electrode material. In some examples,the negative electrode material wets into a foam (or porous) structureof the negative current collector. Concurrently, positive electrodematerial from the positive electrode dissolves into the electrolyte ascations of the positive electrode material (e.g., Pb²⁺, Sn²⁺, Zn²⁺,Hg²⁺). The concentration of the cations of the positive electrodematerial can vary in vertical proximity within the electrolyte (e.g. asa function of distance above the positive electrode material) based onthe atomic weight and diffusion dynamics of the cation material in theelectrolyte. In some examples, the cations of the positive electrodematerial are concentrated in the electrolyte near the positiveelectrode.

Electrochemical cells of the disclosure can include housings that may besuited for various uses and operations. A housing can include one cellor a plurality of cells. A housing can be configured to electricallycouple the electrodes to a switch, which can be connected to theexternal power source and the electrical load. The cell housing mayinclude, for example, an electrically conductive container that iselectrically coupled to a first pole of the switch and/or another cellhousing, and an electrically conductive container lid that iselectrically coupled to a second pole of the switch and/or another cellhousing. The cell can be arranged within a cavity of the container. Afirst one of the electrodes of the cell can contact and be electricallycoupled with an endwall of the container. An electrically insulatingseal (e.g., bonded ceramic ring) may electrically isolate negativepotential portions of the cell from positive portions of the container(e.g., electrically insulate the negative current lead from the positivecurrent lead). In an example, the negative current lead and thecontainer lid (e.g., cell cap) can be electrically isolated from eachother, where a dielectric sealant material can be placed between thenegative current lead and the cell cap. As an alternative, a housingincludes an electrically insulating sheath (e.g., alumina sheath) orcorrosion resistant and electrically conductive sheath or crucible (e.g.graphite sheath or crucible). In some cases, a housing and/or containermay be a battery housing and/or container.

Electrochemical Cells

A battery, as used herein, can comprise a plurality of electrochemicalcells. Individual cells of the plurality can be electrically coupled toone another in series and/or in parallel. In serial connectivity, thepositive terminal of a first cell is connected to a negative terminal ofa second cell. In parallel connectivity, the positive terminal of afirst cell can be connected to a positive terminal of a second, and/oradditional, cell(s).

Reference will now be made to the figures, wherein like numerals referto like parts throughout. It will be appreciated that the figures andfeatures therein are not necessarily drawn to scale.

With reference to FIG. 1, an electrochemical cell (A) is a unitcomprising an anode and a cathode. The cell may comprise an electrolyteand be sealed in a housing as described herein. In some cases, theelectrochemical cells can be stacked (B) to form a battery (i.e., acompilation of electrochemical cells). The cells can be arranged inparallel, in series, or both in parallel and in series (C).

Electrochemical cells of the disclosure may be capable of storing and/orreceiving input of (“taking in”) substantially large amounts of energy.In some instances, a cell is capable of storing and/or taking in about 1Watt-hour (Wh), about 5 Wh, 25 Wh, about 50 Wh, about 100 Wh, about 500Wh, about 1 kilowatt-hour (kWh), about 1.5 kWh, or about 2 kWh. In someinstances, the battery is capable of storing and/or taking in at leastabout 1 Wh, at least about 5 Wh, at least about 25 Wh, at least about 50Wh, at least about 100 Wh, at least about 500 Wh, at least about 1 kWh,at least about 1.5 kWh, at least about 2 kWh, at least about 3 kWh, atleast about 5 kWh, at least about 10 kWh, at least about 15 kWh, atleast about 20 kWh, at least about 30 kWh, at least about 40 kWh, or atleast about 50 kWh. A cell can be capable of providing a current at acurrent density of at least about 10 mA/cm², 20 mA/cm², 30 mA/cm², 40mA/cm², 50 mA/cm², 60 mA/cm², 70 mA/cm², 80 mA/cm², 90 mA/cm², 100mA/cm², 200 mA/cm², 300 mA/cm², 400 mA/cm², 500 mA/cm², 600 mA/cm², 700mA/cm², 800 mA/cm², 900 mA/cm², 1 A/cm², 2 A/cm², 3 A/cm², 4 A/cm², 5A/cm², or 10 A/cm²; where the current density is determined based on theeffective cross-sectional area of the electrolyte and where thecross-sectional area is the area that is orthogonal to the net flowdirection of ions through the electrolyte during charge or dischargeprocesses.

A compilation or array of cells (i.e., battery) can include any suitablenumber of cells, such as at least about 2, at least about 5, at leastabout 10, at least about 50, at least about 100, at least about 500, atleast about 1000, at least about 5000, at least about 10000, and thelike. In some examples, a battery includes 1, 2, 3, 4, 5, 6, 7, 8, 9,10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600,700, 800, 900, 1000, 2000, 5000, 10,000, 20,000, 50,000, 100,000,500,000, or 1,000,000 cells.

Batteries of the disclosure may be capable of storing and/or taking in asubstantially large amount of energy for use with a power grid (i.e., agrid-scale battery) or other loads or uses. In some instances, a batteryis capable of storing and/or taking in about 5 kilowatt-hour (kWh), 25kWh, about 50 kWh, about 100 kWh, about 500 kWh, about 1 megawatt-hour(MWh), about 1.5 MWh, about 2 MWh, about 3 MWh, about 5 MWh, about 10MWh, about 25 MWh, about 50 MWh, or about 100 MWh. In some instances,the battery is capable of storing and/or taking in at least about 1 kWh,at least about 5 kWh, at least about 25 kWh, at least about 50 kWh, atleast about 100 kWh, at least about 500 kWh, at least about 1 MWh, atleast about 1.5 MWh, at least about 2 MWh, at least about 3 MWh, atleast about 5 MWh, at least about 10 MWh, at least about 25 MWh, atleast about 50 MWh, or at least about 100 MWh.

In some instances, the cells and cell housings are stackable. Anysuitable number of cells can be stacked. Cells can be stackedside-by-side, on top of each other, or both. In some instances, at leastabout 10, 50, 100, or 500 cells are stacked. In some cases, a stack of100 cells is capable of storing and/or taking in at least 50 kWh ofenergy. A first stack of cells (e.g., 10 cells) can be electricallyconnected to a second stack of cells (e.g., another 10 cells) toincrease the number of cells in electrical communication (e.g., 20 inthis instance).

An electrochemical energy storage device can include one or moreindividual electrochemical cells. An electrochemical cell can be housedin a container, which can include a container lid (e.g., cell cap) andseal component. The device can include at least 1, 2, 3, 4, 5, 6, 7, 8,9, 10, 20, 30, 40, 50, 100, 200, 300, 400, 500, 1000, 10,000, 100,000 or1,000,000 cells. The container lid may utilize, for example, a seal(e.g., annular dielectric gasket) to electrically isolate the containerfrom the container lid. Such a gasket may be constructed from anelectrically insulating material, such as, for example, glass, oxideceramics, nitride ceramics, chalcogenides, or a combination thereof. Theseal may be made hermetic by one or more methods. For example, the sealmay be subject to relatively high compressive forces (e.g., greater than10,000 psi) between the container lid and the container in order toprovide a seal in addition to electrical isolation. Alternatively, theseal may be bonded through a weld, a braze, or other chemically adhesivematerial that joins relevant cell components to the insulating sealantmaterial.

FIG. 2 schematically illustrates a battery that comprises anelectrically conductive housing 201 and a conductor 202 in electricalcommunication with a current collector 203. The battery of FIG. 2 can bea cell of an energy storage device. The conductor can be electricallyisolated from the housing and can protrude through the housing throughan aperture in the housing such that the conductor of a first cell is inelectrical communication with the housing of a second cell when thefirst and second cells are stacked.

In some cases, a cell comprises a negative current collector, a negativeelectrode, an electrolyte, a positive electrode and a positive currentcollector. The negative electrode can be part of the negative currentcollector. As an alternative, the negative electrode is separate from,but otherwise kept in electrical communication with, the negativecurrent collector. The positive electrode can be part of the positivecurrent collector. As an alternative, the positive electrode can beseparate from, but otherwise kept in electrical communication with, thepositive current collector.

A cell housing can comprise an electrically conductive container and aconductor in electrical communication with a current collector. Theconductor may protrude through the housing through an aperture in thecontainer and may be electrically isolated from the container. Theconductor of a first housing may contact the container of a secondhousing when the first and second housings are stacked.

In some instances, the area of the aperture through which the conductorprotrudes from the housing and/or container is small relative to thearea of the housing and/or container. In some cases, the ratio of thearea of the aperture to the area of the housing is about 0.001, about0.005, about 0.01, about 0.05, about 0.1, about 0.15, about 0.2, orabout 0.3. In some cases, the ratio of the area of the aperture to thearea of the housing is less than or equal to 0.001, less than or equalto 0.005, less than or equal to 0.01, less than or equal to 0.05, lessthan or equal to 0.1, less than or equal to 0.15, less than or equal to0.2, or less than or equal to 0.3.

A cell can comprise an electrically conductive housing and a conductorin electrical communication with a current collector. The conductorprotrudes through the housing through an aperture in the housing and maybe electrically isolated from the housing. The ratio of the area of theaperture to the area of the housing may be less than about 0.3, 0.2,0.15, 0.1, 0.05, 0.01, 0.005, or 0.001.

A cell housing can comprise an electrically conductive container and aconductor in electrical communication with a current collector. Theconductor protrudes through the container through an aperture in thecontainer and is electrically isolated from the container. The ratio ofthe area of the aperture to the area of the container may be less thanabout 0.3, 0.2, 0.15, 0.1, 0.05, 0.01, 0.005, or 0.001. The housing canbe capable of enclosing a cell that is capable of storing and/or takingin less than 100 Wh of energy, about 100 Wh of energy, or more than 100Wh of energy. The cell can be capable of storing and/or taking in atleast about 1 Wh, 5 Wh, 25 Wh, 50 Wh, 100 Wh, 500 Wh, 1 kWh, 1.5 kWh, 2kWh, 3 kWh, 5 kWh, 10 kWh, 15 kWh, 20 kWh, 30 kWh, 40 kWh, or 50 kWh ofenergy.

FIG. 3 is a cross-sectional side view of an electrochemical cell orbattery 300 comprising a housing 301, an electrically conductivefeed-through (i.e., conductor, such as a conductor rod) 302 that passesthrough an aperture in the housing and is in electrical communicationwith a liquid metal negative electrode 303, a liquid metal positiveelectrode 305, and a liquid salt electrolyte 304 between the liquidmetal electrodes 303, 305. The cell or battery 300 can be configured foruse with cell chemistries operated under a low voltage mode (“Type 1mode”) or high voltage mode (“Type 2 mode”), as disclosed elsewhereherein. The conductor 302 may be electrically isolated from the housing301 (e.g., using electrically insulating seals). The negative currentcollector 307 may be foam material that behaves like a sponge, and is“soaked” in negative electrode liquid metal 303. The negative electrode303 is in contact with the molten salt electrolyte 304. The saltelectrolyte is also in contact with the positive liquid metal electrode305. The positive liquid metal electrode 305 can be in electricalcommunication with the housing 301 along the side walls and/or along thebottom end wall of the housing.

The housing may include a container and a container lid (e.g., cellcap). The container and container lid may be connected mechanically. Thenegative current lead may be electrically isolated from the containerand/or container lid (e.g., cell cap), via, for example, the use of anelectrically insulating hermetic seal. In some examples, an electricallyinsulating barrier (e.g., seal) may be provided between the negativecurrent lead and the container lid. As an alternative, the seal can bein the form of a gasket, for example, and placed between the containerlid, and the container. In some examples, the electrochemical cell orbattery 300 may comprise two or more conductors passing through one ormore apertures and in electrical communication with the liquid metalnegative electrode 303. In some instances, a separator structure (notshown) may be arranged within the electrolyte 304 between the liquidnegative electrode 303 and the (liquid) positive electrode 305.

The housing 301 can be constructed from an electrically conductivematerial such as, for example, steel, iron, stainless steel, graphite,nickel, nickel based alloys, titanium, aluminum, molybdenum, tungsten,or conductive compounds such as nitrides. The housing may also comprisea thinner lining component of a separate metal or compound coating, suchas, for example, a steel housing with a graphite lining, or a steelhousing with a boron nitride coating, or titanium coating. The coatingcan exhibit favorable properties and functions, including surfaces thatare anti-wetting to the positive electrode liquid metal. In some cases,the lining (e.g., graphite lining) may be dried by heating above roomtemperature in air or dried in a vacuum oven before or after beingplaced inside the cell housing. Drying or heating the lining may removemoisture from the lining prior to adding the electrolyte, positiveelectrode, or negative electrode to the cell housing.

The housing 301 may include a thermally and/or electrically insulatingsheath 306. In this configuration, the negative electrode 303 may extendlaterally between the side walls of the housing 301 defined by thesheath without being electrically connected (i.e., shorted) to thepositive electrode 305. Alternatively, the negative electrode 303 mayextend laterally between a first negative electrode end 303 a and asecond negative electrode end 303 b. When the sheath 306 is notprovided, the negative electrode 303 may have a diameter (or othercharacteristic dimension, illustrated in FIG. 3 as the distance from 303a to 303 b) that is less than the diameter (or other characteristicdimension such as width for a cuboid container, illustrated in FIG. 3 asthe distance D) of the cavity defined by the housing 301.

The sheath 306 can be constructed from a thermally insulating, thermallyconducting, and/or electrically insulating material such as, forexample, a carbide (e.g., SiC, TiC), nitride (e.g., BN), alumina,titania, silica, magnesia, boron nitride, or a mixed oxide, such as, forexample, calcium oxide, aluminum oxide, silicon oxide, lithium oxide,magnesium oxide, etc. As shown in FIG. 3, the sheath 306 has an annularcross-sectional geometry that can extend laterally between a firstsheath end 306 a and a second sheath end 306 b. The sheath may bedimensioned (illustrated in FIG. 3 as the distance from 306 a to 306 b)such that the sheath is in contact and pressed up against the side wallsof the cavity defined by the housing cavity 301. As an alternative, thesheath can be used to prevent corrosion of the container and/or preventwetting of the cathode material up the side wall, and may be constructedout of an electronically conductive material, such as steel, stainlesssteel, tungsten, molybdenum, nickel, nickel based alloys, graphite,titanium, or titanium nitride. In some cases, the sheath (e.g., graphitesheath) may be dried by heating above room temperature in air or driedin a vacuum oven before or after being placed inside the cell housing.Drying or heating the lining may remove moisture from the lining priorto adding the electrolyte, positive electrode, or negative electrode tothe cell housing.

Instead of a sheath, the cell may comprise an electrically conductivecrucible or coating that lines the side walls and bottom inner surfaceof the cell housing, referred to as a cell housing liner, preventingdirect contact of the positive electrode with the cell housing. The cellhousing liner may prevent wetting of the positive electrode between thecell housing and the cell housing liner or sheath and may prevent directcontact of the positive electrode on the bottom surface of the cellhousing. The sheath may be very thin and can be a coating. The coatingcan cover just the inside of the walls, and/or, can also cover thebottom of the inside of the container. The sheath may not fit perfectlywith the housing 301 which may hinder the flow of current between thecell lining and the cell housing. To ensure adequate electronicconduction between the cell housing and the cell lining, a liquid ofmetal that has a low melting point (i.e. Pb, Sn, Bi) can be used toprovide a strong electrical connection between the sheath/coating andthe cell housing. This layer can allow for easier fabrication andassembly of the cell.

The housing 301 can also include a first (e.g., negative) current lead307 and a second (e.g., positive) current collector 308. The negativecurrent collector 307 may be constructed from an electrically conductivematerial such as, for example, nickel-iron (Ni—Fe) foam, perforatedsteel disk, sheets of corrugated steel, sheets of expanded metal mesh,etc. The negative current collector 307 may be configured as a plate orfoam that can extend laterally between a first collector end 307 a and asecond collector end 307 b. The negative current collector 307 may havea collector diameter that is less than or equal to the diameter of thecavity defined by the housing 301. In some cases, the negative currentcollector 307 may have a collector diameter (or other characteristicdimension, illustrated in FIG. 3 as the distance from 307 a to 307 b)that is less than, equal to, or more than the diameter (or othercharacteristic dimension, illustrated in FIG. 3 as the distance from 303a to 303 b) of the negative electrode 303. The positive currentcollector 308 may be configured as part of the housing 301; for example,the bottom end wall of the housing may be configured as the positivecurrent collector 308, as illustrated in FIG. 3. Alternatively, thecurrent collector may be discrete from the cell housing and may beelectrically connected to the cell housing. In some cases, the positivecurrent collector may not be electrically connected to the cell housing.The present invention is not limited to any particular configurations ofthe negative and/or positive current collector configurations.

The negative electrode 303 can be contained within the negative currentcollector (e.g., foam) 307. In this configuration, the electrolyte layercomes up in contact with the bottom, sides, and/or the top of the foam307. The metal contained in the foam (i.e., the negative electrodematerial) can be held away from the sidewalls of the housing 301, suchas, for example, by the absorption and retention of the liquid metalnegative electrode into the foam, thus allowing the cell to run withoutthe insulating sheath 306. In some cases, a graphite sheath or graphitecell housing liner (e.g., graphite crucible) may be used to prevent thepositive electrode from wetting up along the side walls, which canprevent shorting of the cell.

Current may be distributed substantially evenly across a positive and/ornegative liquid metal electrode in contact with an electrolyte along asurface (i.e., the current flowing across the surface may be uniformsuch that the current flowing through any portion of the surface doesnot substantially deviate from an average current density). In someexamples, the maximum density of current flowing across an area of thesurface is less than about 105%, or less than or equal to about 300%,250%, 200%, 175%, 150%, 125%, or 115% of the average density of currentflowing across the surface. In some examples, the minimum density ofcurrent flowing across an area of the surface is greater than or equalto about 50%, 60%, 70%, 80%, 90%, or 95% of the average density ofcurrent flowing across the surface.

Viewed from a top or bottom direction, as indicated respectively by “TOPVIEW” and “BOTTOM VIEW” in FIG. 3, the cross-sectional geometry of thecell or battery 300 can be circular, elliptical, square, rectangular,polygonal, curved, symmetric, asymmetric or any other compound shapebased on design requirements for the battery. In an example, the cell orbattery 300 is axially symmetric with a circular or squarecross-section. Components of cell or battery 300 (e.g., component inFIG. 3) may be arranged within the cell or battery in an axiallysymmetric fashion. In some cases, one or more components may be arrangedasymmetrically, such as, for example, off the center of the axis 309.

The combined volume of positive and negative electrode material may beat least about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 95%of the volume of the battery (e.g., as defined by the outer-most housingof the battery, such as a shipping container). In some cases, thecombined volume of anode and cathode material is at least about 5%, atleast about 10%, at least about 20%, at least about 40%, at least about60%, or at least about 75% of the volume of the cell. The combinedvolume of the positive and negative electrodes material may grow orshrink (e.g., in height) during operation due to the volume (size)growth or shrinkage of the positive or negative electrode. In anexample, during discharge, the volume of the negative electrode (anodeduring discharge) may be reduced due to transfer of the negativeelectrode material to the positive electrode (cathode during discharge),wherein the volume of the positive electrode is increased (e.g., as aresult of an alloying reaction). The volume reduction of the negativeelectrode may or may not equal the volume increase of the positiveelectrode. The positive and negative electrode materials may react witheach other to form a solid or semi-solid mutual reaction compound (also“mutual reaction product” herein), which may have a density that is thesame, lower, or higher than the densities of the positive and/ornegative electrode materials. Although the mass of material in theelectrochemical cell or battery 300 may be constant, one, two or morephases (e.g., liquid or solid) may be present, and each such phase maycomprise a certain material composition (e.g., an alkali metal may bepresent in the materials and phases of the cell at varyingconcentrations: a liquid metal negative electrode may contain a highconcentration of an alkali metal, a liquid metal positive electrode maycontain an alloy of the alkali metal and the concentration of the alkalimetal may vary during operation, and a mutual reaction product of thepositive and negative liquid metal electrodes may contain the alkalimetal at a fixed or variable stoichiometry). The phases and/or materialsmay have different densities. As material is transferred between thephases and/or materials of the electrodes, a change in combinedelectrode volume may result.

In some cases, a cell can include one or more alloyed products that areliquid, semi-liquid (or semi-solid), or solid. The alloyed products canbe immiscible with the negative electrode, positive electrode and/orelectrolyte. The alloyed products can form from electrochemicalprocesses during charging or discharging of a cell.

An alloyed product can include an element constituent of a negativeelectrode, positive electrode and/or electrolyte. An alloyed product canhave a different density than the negative electrode, positive electrodeor electrolyte, or a density that is similar or substantially the same.The location of the alloyed product can be a function of the density ofthe alloyed product compared to the densities of the negative electrode,electrolyte and positive electrode. The alloyed product can be situatedin the negative electrode, positive electrode, or electrolyte, or at alocation (e.g., interface) between the negative electrode and theelectrolyte or between the positive electrode and the electrolyte. In anexample, an alloyed product is an intermetallic between the positiveelectrode and the electrolyte (see FIG. 4). In other examples, thealloyed product can be at other locations within the cell and be formedof a material of different stoichiometries/compositions, depending onthe chemistry, temperature, and/or charge state of the cell.

FIG. 4 is a cross-sectional side view of an electrochemical cell orbattery 400 with an intermetallic layer 410. The intermetallic layer 410can include a mutual reaction compound of a material originating fromthe negative electrode 403 and positive electrode material 405. An upperinterface 410 a of the intermetallic layer 410 is in contact with theelectrolyte 404, and a lower interface 410 b of the intermetallic layer410 is in contact with the positive electrode 405. The mutual reactioncompound may be formed during discharging at an interface between apositive liquid metal electrode (liquid metal cathode in thisconfiguration) 405 and a liquid metal electrolyte 404. The mutualreaction compound (or product) can be solid or semi-solid. In anexample, the intermetallic layer 410 can form at the interface betweenthe liquid metal cathode 405 and the liquid metal electrolyte 404. Insome cases, the intermetallic layer 410 may exhibit liquid properties(e.g., the intermetallic may be semi-solid, or it may be of a higherviscosity or density than one or more adjacent phases/materials).

The cell 400 comprises a first current collector 407 and a secondcurrent collector 408. The first current collector 407 is in contactwith the negative electrode 403, and the second current collector 408 isin contact with the positive electrode 405. The first current collector407 is in contact with an electrically conductive feed-through 402. Ahousing 401 of the cell 400 can include a thermally and/or electricallyinsulating sheath 406. In an example, a negative liquid metal electrode403 includes magnesium (Mg), the positive liquid metal electrode 405includes antimony (Sb), and the intermetallic layer 410 includes Mg andSb (Mg_(x)Sb, where ‘x’ is a number greater than zero), such as, forexample, magnesium antimonide (Mg₃Sb₂). Cells with a Mg∥Sb chemistry maycontain magnesium ions within the electrolyte as well as other salts(e.g., MgCl₂, NaCl, KCl, or a combination thereof). In a dischargedstate, the cell is deficient in Mg in the negative electrode and thepositive electrode comprises an alloy of Mg—Sb, and during charging, Mgis supplied from the positive electrode, passes through the electrolyteas a positive ion, and deposits onto the negative current collector asMg. In some examples, the cell has an operating temperature of at leastabout 550° C., 600° C., 650° C., 700° C., or 750° C., and in some casesbetween 650° C. and 750° C. In a charged state, all or substantially allthe components of the cell are in a liquid state. Alternativechemistries exist, including Ca—Mg∥Bi comprising a calcium halideconstituent in the electrolyte (i.e. CaCl₂, KCl, LiCl, or combinationsthereof) and operating above 500° C., Li∥Pb—Sb cells comprising alithium halide electrolyte (i.e. LiF, LiCl, LiBr, or combinationsthereof) and operating between 350° C. and 550° C., and Na∥Pb cellscomprising a sodium halide as part of the electrolyte (i.e. NaCl, NaF,LiCl, LiF, LiBr, KCl, KBr, or combinations thereof) and operating above300° C. In some cases, the product of the discharge reaction may be anintermetallic compound (i.e. Mg₃Sb₂ for the Mg∥Sb cell chemistry, Li₃Sbfor the Li∥Pb—Sb chemistry, or Ca₃Bi₂ for the Ca—Mg∥Bi chemistry) wherethe intermetallic layer may develop as a distinct solid phase by growingand expanding horizontally along a direction x and/or growing orexpanding vertically along a direction y at the interface between thepositive electrode and the electrolyte. The growth may be axiallysymmetrical or asymmetrical with respect to an axis of symmetry 409located at the center of the cell or battery 400. Alternatively, thesolid intermetallic layer may develop and expand starting from one ormore locations (also “nucleation sites” herein) along a surface parallelto the direction x (i.e., the interface between the liquid metal cathodeand the liquid metal electrolyte). The nucleation sites may be locatedin a predetermined pattern along the surface; alternatively, thelocation of the nucleation sites may be stochastic (random), ordetermined by natural or induced defects at the interface between theliquid metal cathode and the liquid metal electrolyte, or elsewherewithin the cell or battery 400. In some examples, the solidintermetallic layer may not grow and expand horizontally. For example,the solid intermetallic layer may form evenly across the interface.

The solid intermetallic layer may begin developing at or near a verticallocation corresponding to the location of the upper surface of theliquid metal cathode at the commencement of discharging (i.e., theinterface between the liquid metal cathode and the liquid metalelectrolyte at the commencement of discharging), and may then grow in adownward direction y. Thus, the solid intermetallic layer may have anupper interface or surface 410 a and a lower interface or surface 410 b.The upper interface 410 a may remain in an approximately fixed locationalong the axis 409, while the lower interface 410 b moves in a downwarddirection during discharge. In some cases, the solid intermetallic layermay grow and/or deform in the downward direction (i.e., intermetallicmaterial is added to the layer from the downward direction opposite tovector y). Material buildup along the interface 410 b may cause pressureto build up from below. The pressure may exert a force on theintermetallic layer. The pressure may be hydraulic pressure from theliquid metal cathode 405. In some cases, the pressure may be due tomaterial stresses in the intermetallic layer 410. This may, for example,cause the intermetallic layer 410 to bulge or bow upward (see, forexample, FIG. 7A). In some cases, the liquid metal cathode may breakthrough the intermetallic layer and some liquid metal cathode materialmay eject into the liquid metal electrolyte past the upper surface ofthe intermetallic layer, forming fingers or dendritic outgrowths. Theintermetallic layer may be partially distorted, and may be ruptured orcracked in one or more locations along the interface 410 a.

In some cases, a combination of horizontal and downward growth mayoccur. For example, a layer having a thickness t may develop in adownward direction along the central axis, and expand horizontallyduring discharge at a thickness of less than t, about t, or larger thant. The thickness t may also change as a function of discharge ordischarge time. The morphology of the interfaces 410 a, 410 b may not beas uniform as shown in FIG. 4. For example, the interfaces may be lumpy,jagged, uneven, spongy or have offshoots, fingers or dendriticcharacteristics. For example, the interface 410 a can be undulating.Depending on the lateral extent of the intermetallic layer 410 withrespect to the dimension of the cavity defined by the side walls ofsheath 406 or housing 401 and/or the morphology of the intermetalliclayer 410, one or more interfaces between the liquid metal electrolyte404 and the liquid metal cathode 405 may exist. The interfaces mayprovide a means for reduction reactions to proceed at the liquid metalcathode. The solid intermetallic layer may grow by the addition ofmaterial formed at or near the interfaces.

During discharge, the cathode may comprise the liquid metal cathode 405,and the solid intermetallic layer 410 is formed adjacent to the cathode.As previously described, material can be transferred to the cathodeduring discharge such that the mass of the cathode grows. The cathodevolume may expand as a result of the material addition. The volumeexpansion may be affected by the alloying reaction. For example, thecathode volume increase after alloying may be about 30% less thanexpected from adding together the volume of material added to thecathode and the material originally present in the cathode. In somecases, the densities of the intermetallic layer 410 and the liquid metalcathode 405 may be about the same. Alternatively, the density of theintermetallic layer may be higher or lower than the density of theliquid metal cathode 405. For example, the density of the intermetalliclayer may be a function of the phase structure of the solid formed. Asthe cathode volume increases during discharging, individually, theintermetallic layer 410 may grow, but the liquid metal cathode 405 maybe consumed. The intermetallic layer 410 may grow at the expense of theliquid metal cathode 405. Alternatively, the volumes of both theintermetallic layer 410 and the liquid metal cathode 405 may increase,but the increase in volume of the liquid metal cathode 405 is less thanit would otherwise be in the absence of an intermetallic layer. In someexamples, the alloy in the liquid metal cathode 405, and the alloy inthe intermetallic layer 410 may be formed independently at theinterfaces between the liquid metal electrolyte and the liquid metalcathode. Alternatively, the formation of the intermetallic layer 410 mayconsume alloy first formed in the liquid metal cathode 405. Theexpansion of the liquid metal cathode 405 confined by an intermetalliclayer 410, and the sheath 406 or housing 401 may lead to hydraulicpressure buildup in the liquid metal cathode 405.

With continued reference to FIG. 4, the intermetallic 410 can be locatedbetween the liquid metal electrolyte 404 and the liquid metal cathode405. During normal operation, the cell or battery 400 can be oriented inthe direction shown in FIG. 4, such that any gravitational pullaffecting the cell is oriented downward in the direction of the vectory. A hydrostatic pressure from the liquid metal electrolyte 404 mayexert a downward force (in the direction of y) on the intermetalliclayer 410. This force may remain constant during discharge, as the massof the liquid metal electrolyte may not change. The upper interface 410a of the intermetallic layer may be stationary. As the intermetalliclayer 410 grows, a hydraulic pressure may build up in the liquid metalcathode 405, and may exert an upward force (in the opposite directionfrom y) on the intermetallic layer 410.

Pressure Relief Mechanism for Cathode (Riser Pipes)

An aspect of the disclosure relates to pressure relief mechanisms forelectrochemical cells or batteries. The pressure relief mechanisms canbe applied, for example, in liquid metal batteries described herein.Examples include application of the pressure relief mechanisms topositive battery electrodes in liquid metal batteries (e.g., forpressure relief during battery discharging, when the positive batteryelectrode functions as a cathode). The pressure relief mechanisms may beutilized to improve performance (e.g., charge cycling), longevity and/orto prevent battery failure. In other examples, pressure reliefmechanisms and structures can be applied in alternative systems, suchas, for example, in any energy storage device or energy transformationdevice with a liquid component which may expand and/or contract duringoperation. Operation may include charging, discharging, heating, coolingor any other change in state of the device.

In an illustrative example, pressure relief mechanisms and structuresare provided for a positive electrode, such as the positive liquid metalelectrode 405 in FIG. 4. The positive liquid metal electrode 405 mayexperience an expansive pressure force during discharging. Duringdischarging, the positive liquid metal electrode can function as acathode, and the negative liquid metal electrode 403 can function as ananode. If the liquid cathode cannot freely expand as material istransferred from the anode during discharge (e.g., due to the formationof the solid layer 410 atop the liquid cathode), internal pressure canbuild. This can result in undesirable morphologies (such as bowingdescribed herein) and/or sudden, uncontrolled pressure-induced puncturesor cracks that can inhibit cell operability.

Pressure relief mechanisms disclosed herein provide one or moreunobstructed physical spaces (also “chambers” herein) where the liquidcathode can freely expand and contract during cycling, thus relievingpressure. Thus, the disclosure provides a mechanism for reversiblyrelieving internal fluid pressure.

FIG. 5 is a cross-sectional side view of an electrochemical cell orbattery 500 with a pressure relief structure 511. In an example, thebattery cell 500 can have an axially symmetric, circular cross-sectionwhen viewed from above (“top view” in FIG. 5). The housing 501 can haveconcentric walls 511 a, 511 b. A first chamber or cavity can include anegative liquid metal electrode 503, a negative current collector 507, aliquid metal electrolyte 504, a positive liquid metal electrode 505 anda positive current collector 508. During discharge, a solidintermetallic layer 510 may form, as described elsewhere herein. Thepressure relief structure 511 forms a second chamber. The walls of thefirst and second chambers can form the concentric walls of the housing501 which may include a container, as described elsewhere herein. Thus,the pressure relief structure 511 is provided in the annular chamber(also referred to as “riser pipe” herein) defined by the concentricwalls. In some cases, the concentric walls of the housing may beintegrally formed. Alternatively, the concentric walls may be formedseparately and mechanically joined, e.g., by welding. The housing and/orthe walls can be formed of any materials for housings/containersdescribed herein.

During discharge, the negative liquid metal electrode 503 can be ananode and the positive liquid metal electrode 505 can be a cathode. Theintermetallic layer 510 includes an upper interface 510 a and a lowerinterface 510 b. As the lower interface 510 b of the intermetallic layer510 moves in a downward direction indicated by arrows 512, the liquidmaterial of the cathode 505 is compressed. When pressure builds due toactive electrochemistry in the first chamber space, the cathode materialcan rise between the walls 511 a, 511 b of the pressure relief structure511 via one or more openings 513 a, 513 b, 514 a, 514 b. The openingscan be provided adjacent to the housing 501 (e.g., openings 513 a, 513b) such that the inner wall 511 a of the pressure relief structure isnot in contact with the bottom wall of the housing 501. In someexamples, the bottom wall can be the positive current collector 508. Theopenings can also be provided at some predetermined distance from thebottom wall of the housing 501 (e.g., openings 514 a, 514 b). Forexample, the inner wall 511 a can be attached to the bottom wall of thehousing and only have openings 514 a, 514 b.

The holes may be circular or of any other shape allowing the cathodematerial to flow through the holes. For example, circular holes may bepreferred to minimize drag on the flowing cathode material. The cathodematerial may flow through the holes as indicated by arrows 515, andupward in the pressure relief structure as indicated by arrows 516.

Combinations and/or a plurality of openings 513 a, 513 b, 514 a, 514 bcan be provided along the inner wall of the annular pressure reliefchamber 511. The holes may be provided at different axial distances fromthe bottom wall of the housing and may be of varying size. For example,the holes may be spaced to prevent the intermetallic layer 510 from“bottoming out”, i.e., from reaching the uppermost level of the holes(which may be near the bottom of the first chamber), and blocking theriser pipe inlet (the area around arrows 515).

The pressure relief structure can have a top wall 511 e. The top wall511 e can close the pressure relief structure to prevent material insidethe riser pipe from spilling over the top of the riser pipe. In somecases, the wall 511 b may be formed separately from the housing. Forexample, the walls 511 a, 511 b, and 511 e can be integrally formed asan annular tube with a closed top and an open bottom (e.g., openings 513a, 513 b), or as an annular tube with closed top and bottom but withperforations or holes near the bottom (e.g., openings 514 a, 514 b). Insome examples, one or more parts or all of the pressure relief structuremay be formed of one or more materials different than the housing 501.One or more parts or all of the pressure relief structure may be formedof an electrically insulating material, such as the electricallyinsulating materials described elsewhere herein.

With continued reference to FIG. 5, the cathode material in the riserpipe is not in contact with to the electrolyte 504. Further, the cathodematerial is electrically isolated from the electrolyte and the anode.When the cathode material is electrically conductive (e.g., a liquidmetal cathode material), the cathode material in the riser pipe (secondchamber) can be electrically connected with the cathode material in thefirst chamber. In some cases, such as, for example, when an unsheathedhousing is employed as described elsewhere herein, only the wall 511 bmay be electrically insulating; the walls 511 b and 511 e may beelectrically conductive. The wall 511 e may only be electricallyconductive if it is to not contact the electrolyte at any point.

The cathode material may rise in the pressure relief structure 511 to aheight h. The height h may vary around the circumference of the pressurerelief structure. The height h can be related to the volume change ofthe cathode (i.e., the liquid and solid cathode materials 505 andintermetallic layer 510). For example, the cathode materials 505 and 510can have a volume V₁ when charged, and a volume V₂ when discharged. Theheight h can be related to the volume difference V₂−V₁ and thecross-sectional area of the pressure relief structure. The annularpressure relief structure in FIG. 5 can have a width w, and an arearelated to w and the circumference of the annular structure. Thedimensions of the pressure relief structure, e.g., w, may be such thatthe cathode material can easily enter and rise in the structure. Forexample, the pressure relief structure can be dimensioned to minimizecapillary wicking effects, and to ensure that the cathode materialexperiences minimal drag forces. The pressure relief structure can bedimensioned to accommodate a predetermined amount of cathode material.For example, the pressure relief structure may be dimensioned toaccommodate less than 10%, less than 25%, less than 50%, or less than75% of maximum volume or mass of the cathode material or of the liquidcathode material.

In some cases, the addition of the riser pipe decreases the gap betweena first negative electrode end 503 a and an adjacent wall (e.g., thewall 511 a in FIG. 5), which may contribute to enhanced side wall creepof the liquid cathode material. To prevent the cathode material fromclimbing the pressure relief structure 511 along the wall facing thefirst chamber and shorting to the anode from the sides (i.e., climbingupward in FIG. 5, parallel and on the opposite side of the wall 511 afrom the arrows 516), the pressure relief structure(s) may be isolatedfrom the anode by a sheath (e.g., carbon or metal nitride or othersheath materials described herein) or coating of material (e.g., PVD orCVD coating of a high temperature material), which is not readily wet bythe cathode material. In some cases, the material may provide a surfacetexture or chemistry that interacts with the intermetallic material,e.g., the intermetallic may easily slide along the surface.

Conversely, one or more parts of the pressure relief structure, e.g.,the surfaces defining the chamber of the riser pipe, may be formed ofand/or coated with a material that is readily wet by the cathode toensure smooth flow of the cathode material in the riser pipe. Thematerial can be inert. In some cases, the material may have desiredreactivity with the cathode material. In some cases, the inlet and/orthe openings 513 a, 513 b, 514 a, 514 b can be coated with a materialthat prevents the intermetallic from sliding into the riser pipe. Theinlet and/or the openings 513 a, 513 b, 514 a, 514 b may be covered witha mesh. The inlet and/or the openings 513 a, 513 b, 514 a, 514 b maycomprise one or more valves or valve-like features. For example, theinlet and/or the openings can be configured to allow flow into the riserpipe above a certain hydraulic pressure value (e.g., duringdischarging), and to allow flow from the riser pipe into the firstchamber (e.g., during charging) at a relatively lower pressure.

Alternative configurations of the pressure relief mechanism may includeexternal pressure relief structures, such as, for example, a riser pipemounted externally to the housing 501 and in fluid communication withthe first chamber via one or more the openings 513 a, 513 b, 514 a, 514b, ducts or connectors. Further examples of pressure relief structuresinclude a shelf with an enlarged area for the intermetallic to grow(FIG. 6A), mechanical crumple zones which can contract and expand as anaccordion (FIG. 6B), and a cell design including flexibility or “give”of the cell body or housing.

With reference to FIG. 6A, an electrochemical cell or battery 600comprises a housing 601, a conductive feed-through (i.e., conductor,such as a conductor rod) 602 that passes through an aperture in thehousing 601 and is in electrical communication with a liquid metalnegative electrode 603. The cell 600 further comprises a liquid metalpositive electrode 605, and a liquid metal electrolyte 604 between theelectrodes 603, 605. The cell comprises a negative current collector 607and a positive current collector 608 that are in electricalcommunication with the negative electrode 603 and positive electrode605, respectively. During discharge of the cell 600, a solid (orsemi-solid) intermetallic layer 610 forms adjacent to the positiveelectrode 605. The intermetallic layer can develop by growinghorizontally along an interface of the electrolyte 604 and the positiveelectrode 605. The expansion may be axially symmetrical or asymmetricalwith respect to an axis of symmetry 609. The electrolyte 604 andintermetallic layer 610 meet at a first interface 610 a, and theintermetallic layer 610 and the positive electrode 605 meet at a secondinterface 610 b. During discharge of the cell 600, the intermetalliclayer 610 can bow, distort or move along a direction indicated by arrows612. The housing 601 can include a shelf or cavity to house theintermetallic layer 610 upon growth of the intermetallic layer 610during discharge of the cell 600. The cavity can be aligned with abottom portion of the housing 601 (as shown). The cavity can include awall portion that expands into a void space (white dashed lines) whenthere is a build-up of pressure in the positive electrode 605. The wallportion can be spring loaded, for example, to (1) provide a resistiveforce to prevent the wall portion from expanding if the pressure in thepositive electrode 605 is below a given pressure, (2) enable the wallportion to expand the pressure in the positive electrode 605 is at orabove the given pressure, and (3) provide a restorative force to returnthe wall portion to its original position when the pressure in thepositive electrode 605 has decreased to below the given pressure. As analternative, the cavity can be aligned with an interface between theelectrolyte 604 and the cathode 605.

With reference to FIG. 6B, in an alternative configuration, the housing601 includes mechanical crumple zones (dashed lines) that can expand andcontract upon growth and shrinkage of the intermetallic layer 610 duringdischarge and charge, respectively, of the cell 600. The crumple zonescan include voids that enable the electrodes 603, 605 and electrolyte604 to flow into upon expansion of the electrodes 603, 605 andelectrolyte 604.

Pressure relief can be readily applied to cells or batteries of varioussize scales. In an example, the annular riser pipe in FIG. 5 isimplemented in a nominal 4 inch, nominal 20 Ah cell (D1=2.75 inches, w=6mm wide, D1+w=3.03 inches, D2=3.5 inches) with Li∥Sb,Pb chemistry with anegative liquid metal electrode (anode during discharge) comprising 9.5grams of Li, a positive liquid metal electrode (cathode duringdischarge) comprising 361.5 grams of 40:60 mol % Sb:Pb, a liquid metalelectrolyte comprising 219.5 grams of 22:31:47 mol % LiF:LiCl:LiBr, anda solid intermetallic layer comprising Li₃Sb formed at an interface ofthe liquid metal electrolyte and the positive liquid metal electrodeduring discharge. The liquid Pb alloy is allowed to “rise up” into theannular riser pipe as a result of expansion of the positive liquid metalelectrode due to a pressure buildup. The concentric wall design iseffective at relieving cathode pressure, and the amount of materialbetween the walls is consistent with the volume expansion expected fromLi alloying with Sb,Pb. Analogously, during charging, the material inthe riser pipe can reversibly contract from the riser pipe. Otherexamples of cell sizes include, for example, a nominal 16 inch cell.

Mechanical Modification of Intermetallic Shape and Morphology

In another aspect of the disclosure, mechanical modifications ofelectrochemical cells (or batteries) are provided. The mechanicalmodifications can be applied, for example, in liquid metal batteriesdescribed herein. Examples include application of the mechanicalmodifications to positive battery electrodes in liquid metal batteries,e.g., for controlling interfaces during battery discharging, when thepositive battery electrode functions as a cathode. The mechanicalmodifications may be utilized to improve battery performance (e.g.,charge cycling), battery longevity and/or to prevent certain batteryfailure modes. In other examples, mechanical modifications can beapplied in alternative systems, such as, for example, in any energystorage device or energy transformation device with multiple phases(e.g., between a liquid and a solid) and phase interfaces which, whereinthe phases and phase interfaces may be formed and/or transformed duringoperation. Operation may include charging, discharging, heating, coolingor any other change in state of the device.

In an example, mechanical modifications are provided for a positiveelectrode, such as the positive liquid metal electrode 405 in FIG. 4.During discharging, the positive liquid metal electrode can function asa cathode, and the negative liquid metal electrode 403 can function asan anode. As described elsewhere herein, the solid layer 410 may formatop the liquid cathode during discharge, and pressure forces from theliquid metal cathode and/or internal stresses in the layer itself maycause undesirable morphologies of the solid layer 410, e.g., bowing orbulging of the solid layer, and/or sudden, uncontrolled pressure-inducedcracks that can inhibit cell operability.

FIG. 7A a cross-sectional side view of an electrochemical cell 700 witha bowing or bulging solid intermetallic layer 710 formed adjacent to apositive liquid metal electrode 705 during discharging, as describedelsewhere herein. In an example, the battery cell 700 can have anaxially symmetric, circular cross-section when viewed from above (“topview” in FIG. 7A). The battery cell can comprise a negative liquid metalelectrode 703, a negative current collector 707, a liquid metalelectrolyte 704, the positive liquid metal electrode 705 and a positivecurrent collector 708. Uncontrolled and unintended formation of theintermetallic layer 710 may cause failure of electrochemical cells orbatteries (e.g., liquid metal battery cells with chemistries such asLi∥Sb,Pb), because the intermetallic solid can grow into structures thatform a short between a negative liquid metal electrode 703 and/or anegative current collector 707 and the positive liquid metal electrode705. During discharge, the negative liquid metal electrode 703 can be ananode and the positive liquid metal electrode 705 can be a cathode.

The cathode morphology may depend on the size of the cell or battery700. In smaller cells (e.g., a nominal 4 inch liquid metal battery cellwith Li∥Sb,Pb chemistry), the cathode morphology may include an bulged(bowed) intermetallic layer with a maximum height at or near the centerof the cell, as shown in FIG. 7A. The liquid metal cathode 705 can fillcell cavity below the arc (i.e., between the intermetallic layer 710,and the bottom wall of the housing 701 and/or the positive currentcollector 708). In larger cells, the intermetallic layer may developirregular undulations with several height maxima distributed over anactive surface or interface (e.g., the interface between the electrolyte704 and the liquid metal cathode 705) of the cell. In some cases, theseundulating morphologies may be problematic during cell operation,because the crests of the undulating cathode (i.e., the undulatingintermetallic layer of the cathode) can contact the anode 703 and/or thenegative current collector 707, which can irreversibly short a cell. Insome examples, the troughs of the undulating features appear to bepinned at the sidewalls of the cell (i.e., at the sidewalls of thehousing 701). In one example, the cathode morphology in a nominal 1 inchliquid metal battery cell with Li∥Sb,Pb chemistry can be relatively flatand controlled, while deviation from flatness can increase withincreasing cell size.

FIG. 7B is a cross-sectional side view of the electrochemical cell orbattery 700 outfitted with a mechanical modification, such as a post717. The added mechanical modification (e.g., an appropriate physicalprotrusion) may interact with the cathode-intermetallic interface(including the intermetallic), thereby modifying thecathode-intermetallic morphology into a form more amenable to extendedcell operation (e.g., encouraging a more flat, uniform intermetalliclayer) by introducing additional pin or “attachment points” in additionto the sidewalls of the housing. Thus, the intermetallic can be allowedto form, but the shape or geometry can be disrupted such that the formedintermetallic layer is flatter (e.g., by forming smaller bulges orundulations). For example, the intermetallic can be forced to formsmaller and lower bulging features (FIG. 7B) between attachment pointsinstead of the single feature across an entire width, diameter or othercharacteristic dimension D of the cell (FIG. 7A). The presence of one ormore disruptors or an array of disruptors may furthermore affect thethickness of the intermetallic layer and/or location of the heightmaxima. For example, a height maximum may not occur symmetricallybetween attachment points, and may depend on the type of attachmentpoint (e.g., the location of a height maximum between a wall attachmentpoint and a post attachment point may be skewed toward one of the twoattachment points). In some cases, a complicated morphology of theintermetallic layer may result from the use of a set or an array ofattachment points. In another example, the intermetallic layer may bethinner near an attachment point, or the thickness may depend on thetype of attachment point.

One or more mechanical modifications (also “disruptors” or“intermetallic disruptors” herein) may be provided in the cell orbattery 700, including, but not limited to, one or more vertical posts,an array of vertical posts (e.g., two, three or more posts 717, a bed ofnails), one or more plates, a grid of interleaved plates configured toform compartments on the cathode (e.g., egg carton-like or grid-likestructure), one or more structural pieces, an array of structural pieces(e.g., an array of angled iron pieces lying on their side on the cellbottom), stamped structures (e.g., stamped ridges) and/or othermechanical disruptor type or configuration capable of mechanicallyinterfering with the growth of the intermetallic layer to enablemanaging the cathode morphology during cycling. In some cases, one ormore features may be provided elsewhere within the cell 700 that arecomplementary to a particular cathode disruptor configuration or to acell morphology that results from a particular cathode disruptorconfiguration. For example, if a stamped ridge configuration or an arrayof posts is used on the cathode, giving rise to a particular wave-likepattern, the negative current collector 707 may be formed with a similarwave-like pattern such that the distance between any point on an uppersurface of the intermetallic layer 710 and a vertically opposite (i.e.,at the same position x) point on the negative current collector 707remains approximately constant across the cell.

FIG. 7C is a cross-sectional side view of the electrochemical cell orbattery 700 outfitted with ridges 718, another example of a mechanicalmodification of the cathode. Although a flat layer is shown, theintermetallic layer may have a morphology determined by the ridgestructure. The disruptors may be formed of any suitable materialincluding, but not limited to, materials suitable forhousings/containers, current collectors, sheaths, or any other featuresof the disclosure. Individual disruptors and/or disruptor types may ormay not be formed of the same material(s). The disruptors may beprovided together with one or more components of cell 700. For example,the disruptors may be provided on bottom wall of the housing 701 and/oron the positive current collector 708. One or more disruptor featuresmay be integrated with one or more cell components, while one or moreother disruptor features may be integrated with another one or more cellcomponents. The disruptor features or parts thereof may be formedseparately and subsequently attached to one or more cell components.Alternatively, the disruptor features or parts thereof may be integrallyformed with one or more cell components. For example, ridges may bestamped into the positive current collector 708, and an additionaldisruptor grid may be attached to or contacted with the modifiedpositive current collector, thus forming a composite disruptorconfiguration. In another example, a first portion of a single type ofdisruptor may be integrally formed with the housing 701, while a secondportion may be attached to the first portion during cell assembly. Anycombination of disruptor material, formation or assembly can be used.Furthermore, mechanical modification can be advantageously incorporatedinto an existing cell manufacturing process. For example, ridges orposts can be introduced during stamping or hydroforming of a cellbottom. In another example, the attachment and welding of posts can beautomated or achieved using a robot.

Individual disruptor features (e.g., individual posts) may be spacedapart in a predetermined pattern. For example, a spacing betweenindividual disruptor features in array can be determined to achieve apredetermined maximum height and/or a predetermined pattern of theintermetallic layer. Once an appropriate spacing is determined, thearray spacing may be scaled between different cell geometries. Forexample, the same spacing can be used, or the spacing can be scaled bycell diameter or width, cell area, etc. In some cases, array spacing canbe scaled according to current density and/or other cell operatingparameters. The disruptor features may be spaced apart uniformly, orstochastically. The disruptor features may be spaced apart to achieve adesired surface density of disruptor features (e.g., an average surfacedensity of 1.5 posts per square centimeter of the bottom surface of thehousing 701).

In an example, the disruptor of FIG. 7B is implemented in a nominal 4inch, nominal 20 Ah cell (D1=2.75 inches, w=6 mm wide, D1+w=3.03 inches,D2=3.5 inches) with Li∥Sb,Pb chemistry with a negative liquid metalelectrode (anode during discharge) comprising 15.8 grams of Li, apositive liquid metal electrode (cathode during discharge) comprising480.3 grams of 40:60 mol % Sb:Pb, a liquid metal electrolyte comprising300.2 grams of 22:31:47 mol % LiF:LiCl:LiBr, and a solid intermetalliclayer comprising Li₃Sb formed at an interface of the liquid metalelectrolyte and the positive liquid metal electrode during discharge. Ina discharged state, the Li∥Sb,Pb cell can have a intermetallic phase anda metallic Sb,Pb alloy. In experiments with a centered steel post designand an off-center steel post design, the peak of the intermetallic layeris translated from the center of the cell as a result of the presence ofthe post. In the case of the off-center post design, the maximum heightof the bulging intermetallic layer can be shifted in the direction ofthe post, and the intermetallic layer can be thinnest near the post. Anarray of vertical posts extending from the cell bottom and a grid ofinterleaved metal plates, producing several compartments in the cellbottom similar to an egg carton have also been tested. Other examples ofcell sizes include, for example, a nominal 16 inch cell.

Aspects of the disclosure may be synergistically combined. For example,a pressure relief mechanism can be used in concert with otherintermetallic management strategies, such as the use of mechanicaldisruptors described herein. The pressure relief mechanism may enhancethe performance of the disruptors by reducing the tendency of cathodematerial to be forced through induced defects in the intermetalliclayer. For example, in Li∥Sb,Pb systems, the use of disruptors alone maycause defects in the solid intermetallic layer that do not result in acontrolled pressure release, causing liquid cathode material to breakthrough the defects with substantial force. The resulting upward motionof liquid cathode material can be a limiting factor to cell operabilityand lifespan. The use of pressure relief mechanisms of the disclosuremay alleviate the pressure buildup and enable improved (or modified)disruptor performance. For example, smaller and/or otherwise distributeddisrupters may be used during operation with lesser pressure buildup.

Any aspects of the disclosure described in relation to cathodes mayequally apply to anodes at least in some configurations. Similarly, oneor more battery electrodes and/or the electrolyte may not be liquid inalternative configurations. In an example, the electrolyte can be apolymer or a gel. In a further example, at least one battery electrodecan be a solid or a gel. Furthermore, in some examples, the electrodesand/or electrolyte may not include metal. Aspects of the disclosure areapplicable to a variety of energy storage/transformation devices withoutbeing limited to liquid metal batteries.

Electrochemical cells of the disclosure may be capable of storing(and/or taking in) a suitably large amount of energy. In some instances,a cell is capable of storing (and/or taking in) about 1 Wh, about 5 Wh,25 Wh, about 50 Wh, about 100 Wh, about 500 Wh, about 1 kWh, about 1.5kWh, about 2 kWh, about 3 kWh, or about 5 kWh. In some instances, thebattery is capable of storing (and/or taking in) at least about 1 Wh, atleast about 5 Wh, at least about 25 Wh, at least about 50 Wh, at leastabout 100 Wh, at least about 500 Wh, at least about 1 kWh, at leastabout 1.5 kWh, at least about 2 kWh, at least about 3 kWh, or at leastabout 5 kWh. It is recognized that the amount of energy stored in anelectrochemical cell and/or battery may be less than the amount ofenergy taken into the electrochemical cell and/or battery (e.g., due toinefficiencies and losses).

The compilation of cells (i.e., battery) can include any suitable numberof cells, such as at least about 2, at least about 5, at least about 10,at least about 50, at least about 100, at least about 500, at leastabout 1000, at least about 5000, at least about 10000, and the like. Insome examples, a battery includes 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20,30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900,1000, 2000, 5000, 10,000, 20,000, 50,000, 100,000, 500,000, or 1,000,000cells.

Batteries of the disclosure may be capable of storing a suitably largeamount of energy for use with a power grid (i.e., a grid-scale battery)or other loads or uses. In some instances, a battery is capable ofstoring (and/or taking in) about 5 kWh, 25 kWh, about 50 kWh, about 100kWh, about 500 kWh, about 1 MWh, about 1.5 MWh, about 2 MWh, about 3MWh, or about 5 MWh. In some instances, the battery is capable ofstoring (and/or taking in) at least about 5 kWh, at least about 25 kWh,at least about 50 kWh, at least about 100 kWh, at least about 500 kWh,at least about 1 MWh, at least about 1.5 MWh, at least about 2 MWh, atleast about 3 MWh, or at least about 5 MWh.

In some instances, the cells and cell housings are stackable. Anysuitable number of cells can be stacked. Cells can be stackedside-by-side, on top of each other, or both. In some instances, at leastabout 10, 50, 100, or 500 cells are stacked. In some cases, a stack of100 cells is capable of storing at least 50 kWh of energy. A first stackof cells (e.g., 10 cells) can be electrically connected to a secondstack of cells (e.g., another 10 cells) to increase the number of cellsin electrical communication (e.g., 20 in this instance). In someinstances, the energy storage device comprises a stack of 1 to 10, 11 to50, 51 to 100, or more electrochemical cells.

The electrochemical cells can be arranged in series and/or parallel toform an electrochemical energy storage system (i.e., battery). Theenergy storage system can comprise modules, packs, cores, and/or pods ofelectrochemical cells surrounded by a frame.

A person of skill in the art will recognize that the battery housingcomponents may be constructed from materials other than the examplesprovided above. One or more of the electrically conductive batteryhousing components, for example, may be constructed from metals otherthan steel and/or from one or more electrically conductive composites.In another example, one or more of the electrically insulatingcomponents may be constructed from dielectrics other than theaforementioned glass, mica and vermiculite. The present inventiontherefore is not limited to any particular battery housing materials.

Systems, apparatuses and methods of the disclosure may be combined withor modified by other systems, apparatuses and/or methods, such asbatteries and battery components described in U.S. Pat. No. 3,663,295(“STORAGE BATTERY ELECTROLYTE”), U.S. Pat. No. 8,268,471 (“HIGH-AMPERAGEENERGY STORAGE DEVICE WITH LIQUID METAL NEGATIVE ELECTRODE ANDMETHODS”), U.S. Patent Publication No. 2011/0014503 (“ALKALINE EARTHMETAL ION BATTERY”), U.S. Patent Publication No. 2011/0014505 (“LIQUIDELECTRODE BATTERY”), and U.S. Patent Publication No. 2012/0104990(“ALKALI METAL ION BATTERY WITH BIMETALLIC ELECTRODE”), which areentirely incorporated herein by reference.

Energy storage devices of the disclosure may be used in grid-scalesettings or stand-alone settings. Energy storage device of thedisclosure can, in some cases, be used to power vehicles, such asscooters, motorcycles, cars, trucks, trains, helicopters, airplanes, andother mechanical devices, such as robots.

It is to be understood that the terminology used herein is used for thepurpose of describing specific embodiments, and is not intended to limitthe scope of the present invention. It should be noted that as usedherein, the singular forms of “a”, “an” and “the” include pluralreferences unless the context clearly dictates otherwise. In addition,unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention. It is intended thatthe following claims define the scope of the invention and that methodsand structures within the scope of these claims and their equivalents becovered thereby.

What is claimed is:
 1. An energy storage device, comprising: (a) a firstelectrode comprising a first material, a second electrode comprising asecond material, and a liquid electrolyte between said first and secondelectrodes, wherein in a charged state, said first electrode is an anodeand said second electrode is a cathode, and wherein said liquidelectrolyte is capable of conducting ions of said first material; (b) anintermetallic layer disposed at an interface between said secondelectrode and said electrolyte, wherein said intermetallic layer isformed of said first and second materials; and (c) a crucible or coatingsurrounding said first electrode, said second electrode, saidelectrolyte and said intermetallic layer, wherein said crucible orcoating is non-wetting with respect to said second material.
 2. Theenergy storage device of claim 1, wherein said crucible comprisesgraphite.
 3. The energy storage device of claim 1, wherein saidintermetallic layer contacts said crucible or coating.
 4. The energystorage device of claim 1, wherein said crucible or coating lines aninterior of a housing of said energy storage device.
 5. The energystorage device of claim 4, wherein said energy storage device isconfigured such that, during operation, said second electrode does notflow between said crucible and said housing.
 6. The energy storagedevice of claim 4, wherein said coating is bonded to an inner surface ofsaid housing.
 7. The energy storage device of claim 4, wherein saidcrucible is not a sheath.
 8. The energy storage device of claim 1,wherein said crucible or coating is electrically conductive.
 9. Theenergy storage device of claim 1, wherein said second material comprisesat least one Group 12 element.
 10. The energy storage device of claim 1,wherein said second material comprises zinc, cadmium, mercury, aluminum,gallium, indium, silicon, germanium, tin, lead, arsenic, bismuth,antimony, tellurium, selenium, or any combination thereof.
 11. An energystorage device, comprising: (a) a first electrode comprising a firstmaterial; (b) a second electrode comprising a second material; and (c) aliquid electrolyte between said first and second electrodes, whereinsaid liquid electrolyte is capable of conducting ions from said firstmaterial, wherein said energy storage device is configured such that,upon discharge of said energy storage device, said first and secondmaterials react to form an intermetallic layer at an interface betweensaid second electrode and said electrolyte.
 12. The energy storagedevice of claim 11, wherein said second electrode comprises Sb and Pb ata ratio (mol %) of about 40:60 Sb to Pb.
 13. The energy storage deviceof claim 11, wherein said first material comprises an alkali metal, andwherein said second material comprises one or more of a metal, ametalloid or a non-metal.
 14. The energy storage device of claim 13,wherein said second material includes a metalloid, and wherein saidintermetallic layer includes said metalloid.
 15. The energy storagedevice of claim 14, wherein said first material includes lithium, saidsecond material includes antimony, and said intermetallic layer includeslithium antimonide.
 16. The energy storage device of claim 11, whereinsaid first electrode and/or said second electrode are liquid.
 17. Theenergy storage device of claim 11, wherein said intermetallic layercomprises an alkali metal.
 18. The energy storage device of claim 11,wherein said intermetallic layer comprises said first material and saidsecond material.
 19. The energy storage device of claim 11, wherein saidintermetallic layer is a solid.